The exchange anisotropy field, along with the qualitative distribution of the local pinning field at the ferromagnetic/antiferromagnetic interface, has been studied in polycrystalline CoFe/IrMn bilayers. The exchange anisotropy was studied using both the anisotropic magnetoresistance(AMR) technique and hysteresis loop measurements. The AMR technique determines a larger value for the exchange anisotropy than the hysteresis loop technique. It is observed that extracted via the AMR technique for the majority of samples shows a quantifiable dependence on the applied measurement field, even at fields much less than the exchange biasmeasured by hysteresis loop. It is believed that a reversible measurement of the soft dispersive moments takes place at these low fields, and that the field dependence is indicative of a distribution of the local magnetization direction.

The as cast CoFeSiB amorphous wire with 135 μm was drawn out to wires with diameters of 84, 64, and 40 μm, respectively. The magnetoimpedance of the hard-drawn wires were investigated in comparison with the as cast one. For the hard-drawn wire of diameter 64 μm, the magnetoimpedance ratio can reach 269.9%. There is a transform of the domain structure from the inner core longitudinal to the circular in hard-drawn wires compared with the as cast one. The frequency dependence of the magnetoimpedance in longitudinal and transverse cases show that both circumferential and longitudinal axial anisotropies may depend on the radial distance from the axis of the wire.

Recently, the giant magnetoimpedance (GMI) effect found in amorphous wires has been noticed as a method for sensing a magnetic field. The GMI sensor was applied to nondestructive evaluation of microstructural changes for reactor pressure vessel steels passing through the refining process. They were measured by using a GMI sensor and the measured GMI signals were strongly influenced by the microstructural features. The signals are closely related to the grain size, carbide morphology, lath width, and lath boundary that act as a barrier to irreversible domain wall motion.

alloy films, have been fabricated by the magnetron co-sputtering technique. The structure of the films has been studied by x-ray diffraction and transmission electron microscopy. The results indicate the existence of phase in these films. Electric transport and magnetotransport measurements have been performed in the temperature range of 5–300 K and field range of −5–5 T, in which the longitudinal resistivity and extraordinary Hall resistivity have been obtained. A power law dependence of extraordinary Hall resistivity on the longitudinal resistivity, is observed, however the value of the exponent changes from 1 to 1.6 as the temperature changes from 5 to 100 K and above. Different values suggest different mechanisms of the extraordinary Hall effect. The dependence of the Hall resistivity on the Co concentration, x, has also been studied.

A new method for evaluating magnetic interaction among the particles in perpendicular magnetic recording layers under canted magnetic field has been proposed using anomalous Hall effect (AHE) measurement and vibrating sample magnetometer (VSM) measurement. Initial curves and magnetic hysteresis loops were measured to determine an evaluation index to estimate interaction using the relation as The degree of interaction can be determined as a vector by combining the results obtained by VSM and AHE measurements. Distribution of vertices (DOV) of can be regarded as a degree of interaction in a particular direction. The DOV of in Co–Cr–Ta thin film extended along the in-plane direction and showed gradual convergence as the applied field direction canted toward the film plane. This can be an indication that the magnetic particles in the Co–Cr–Ta thin film tend to incline to the applied field direction individually. On the other hand, the DOV of in Co/Pt multilayered thin film extended along the perpendicular direction and the shape of the trajectory of remained unchanged though the applied field direction deviated widely from the normal direction. This may be due to the strong perpendicular anisotropy in the Co/Pt multilayered thin film.

Magnetocapacitance effect of coercive differential spin tunneling junctions fabricated onto a glass substrate by ion-beam mask sputtering was investigated. The impedance was measured by a four-probe method at room temperature in the frequency range from 120 Hz to 1 MHz. It is found that the effective capacitance changes with the application of an external magnetic field. At high frequencies, the magnetocapacitance ratio is as large as the dc magnetoresistance ratio. However, at low frequencies, capacitance changes cannot be observed because the measurement sensitivity is too low. The magnetocapacitance effect was hence found to be a promising tool for high frequency magnetic sensing.

Experiments of the giant magnetoimpedance (GMI) profile have been performed in annealedamorphous ribbons in open air to characterize the role of the bias field on the GMI. The GMI ratio profile measured at 0.1 MHz exhibits a drastic step-like change, the so-called GMI valve, in an 8 h annealed sample at 380 °C. The GMI valve is related to exchange coupling of the bias field with magnetization of the soft amorphous phase, where the bias field is caused by hcp-Co and fcc-Co crystalline phases on the surface B and Si depleted layer. The bias field is stable for an external field less than 100 Oe, but its direction is entirely changed according to the external field over 400 Oe. The GMI profile begins to reveal hysteresis for increasing and decreasing cyclic fields when the maximum field strength exceeds 200 Oe. The peak for the increasing field is positioned in the negative field region, but in the positive field region for decreasing field. This behavior is opposite to general magnetic hysteretic characteristics, suggesting that there is an antiferromagnetic coupling of the bias field with magnetization of the inside amorphous phase.

In this work, results on the giant magnetoimpedance of glass-covered amorphous microwires with nominal composition are presented. The impedance has been investigated as function of frequency (1 MHz–1.8 GHz) and magnetic field (up to ±400 Oe), using a HP4396B impedance analyzer and an appropriate coaxial microwave cavity. The effects of the thermal treatments (Joule heating, from 1 up to 50 mA for 10 min) for anisotropy induction and/or to induce recrystallization have been investigated.

Magnetic properties and Hall resistivity of amorphousfilms depend on the energy of bombarding ions during film growth. The saturation magnetization was found to oscillate with ion energy. The ion bombardment induces in-plane anisotropy and results in a harder perpendicular axis. An exchange field of as high as 95 Oe was observed due to the compositional gradient. The amorphousfilms show a large spontaneous Hall effect. A maximum Hall angle of 1.7% was observed, which is considered to be an important parameter for a Hall device. The large spontaneous Hall resistivity and the low coercivity of the amorphousfilms offer potential applications in weak magnetic-field sensors.

We study the operation of resistively coupled ferromagneticsingle-electron transistors quantitatively. Control of tunnel magnetoresistance on the drain and gate voltages is predicted. Inelastic macroscopic quantum tunneling of charge plays an important role in the enhancement of tunnel magnetoresistance. This implies that the resistively coupled ferromagneticsingle-electron transistors have the possibility as magnetoresistivenanostructuredevices.

Manipulation and detection of magnetic beads on a semiconductor chip opens up new perspectives for analysis of magnetically labeled specimens in biomechanical micro-electromechanical systems for biological applications. Sensitive spin-valvesensors were integrated with magnetic field generating conductors to assess the behavior of ensembles of superparamagnetic nanoparticles 300 nm in diameter that contain 75%–80% magnetite. The spin-valve multilayer including a nanooxide layer achieves 8% magnetoresistance(MR) for an integrated device of Motion of the magnetic particles towards and across the sensor is achieved by two tapered magnetic field generating current conductors. The spin-valvesensor detects the stray magnetic field that emanates from the ensemble of magnetic particles. We study the transients in the magnetic signal on the order of 1% MR. These results lead to a model that describes magnetization configurations of the cluster of beads.

The shape memoryalloy made by melt-spinning method was heat treated in argon in order to investigate the influence of heat treatment on its magnetic property. The specimens after heat treatment were set into the vibration sample magnetometer and the hysteresis loops and the Curie pointtemperature were measured. It can be shown that temperature as was expected has a significant influence on the magnetic and a shape memoryproperty of investigated material.

The magnetoimpedance (MI) effect is based on the change of inductance and resistance under the effect of an external magnetic field. In bulk homogeneous wires or ribbons these two components of the impedance are related to the penetration depth of the electromagnetic field in the material. From simple considerations it is shown that the maximum MI ratio is then proportional to the square root of the relative permeability of the material. That limit is reached for frequencies at which the penetration depth is of the order of the transverse dimensions of the sample. At low operating frequencies, typical of thick geometries, the permeability is limited by the microeddy currents associated with domain wall displacements. The permeability relaxation equivalent to these local eddy currents can be calculated and used in the classical expressions for MI. The real part of the permeability is highly reduced at the relaxation frequency and gives rise to a decrease of the inductance, while the imaginary part contributes to the resistance, with a maximum at the same frequency.